Having spent lots of time and mony building both performance B20's and B21/230's I find that the OHC engines make far more low end torque, even w/o a turbo, and the rate of rise in RPM in a OHC engine can be much quicker that a pushrod engine. There just more of a simple design, without rockers and the cam directyly engages the valve tappet. Also larger displacement is an advantage, and the OHC cylinder head is a much better design to port and modify for performance. You can tune both engines similarly, but the B230 will always make better hp numbers.
On the other hand, I think the B20 is bullet-proof, and is a stronger engine design. As one guy put it, it's like a tractor engine, and can run all day like a work horse.
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'89 245 Sportwagon, '04 V70 2.5T Sportwagon